The invention relates to a method for compensating valve drift in an internal combustion engine having a variable valve drive.
In internal combustion engines which are operated with gas, the necessary mixture mass of air and gas is determined using a volumetric efficiency characteristic diagram. Such engine control functions very reliably with a rigid valve drive.
However, with a variable valve drive changes occur in the valve behavior during the operation of the internal combustion engine. These changes are also referred to as valve drift. These changes can be caused by external influences or by ageing processes in a valve or in the valve control, as a result of which changes occur in the opening behavior or the closing behavior. For example, the changes in the valve behavior can be caused by the hydraulic components or by the masses to be moved. Further causes can be e.g. changes in the friction conditions, wear of the valve plates or surface roughening of the valve plates. As a result, the volumetric efficiency characteristic diagram is no longer up to date and therefore the mixture mass can no longer be determined with sufficient precision. This influences the running behavior of the internal combustion engine and its efficiency. A mixture mass which is adapted to the respective operating conditions of the internal combustion engine gives rise to knocking or misfires.